Switching device for, and a method of switching, a downhole tool

ABSTRACT

The switching device comprises an electronic switch embedded within a downhole tool (100) and an activator for remote switching of the electronic switch. The activator may be a handheld unit that is used at the surface of the wellbore by an operator or may be a wireline run unit. The activator permits wireless and contactless activation of the electronic switch without the need for mechanical switches which could provide a point of failure for the downhole tool. The electronic switch comprises an electronics module and a power source such as one or more batteries wherein in the active configuration, the switch can allow electrical connection between the electronics module and the power source and in the inactive configuration, the switch prevents electrical connection between the electronics module and the power source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of prior U.S. application Ser. No.14/802,402 filed 17 Jul. 2015, which is a continuation of prior U.S.application Ser. No. 12/866,822 filed 6 Mar. 2009 (now U.S. Pat. No.9,103,197), which a national stage under 35 USC 371 of PCT applicationserial no. PCT/GB2009/050227 filed 6 Mar. 2009, which claims priority toUK application serial no. 0804306.9 filed 7 Mar. 2008. The entiredisclosures of these prior applications are incorporated herein by thisreference.

The present invention relates to a switching device for a downhole tool.

Many downhole tools rely on batteries as a source of power. If a tool isassembled with the batteries permanently connected to an electroniccircuit within the tool, battery life can be severely reduced by thetime that the tool is run downhole. This is clearly undesirable sincethe batteries can flatten downhole leaving the tool without a powersource.

In order to conserve battery life some tools are assembled without thebattery connected to an electronic circuit, and a switch is provided toselectively connect the battery on demand. Conventional switches areaccessible from the exterior of the tool allowing an operator to switchthe tool “on” and enable connection of the battery before the tool isrun downhole. An example of one such switch is a mechanical on/offswitch accessible to an operator on the exterior of the tool. The switchis hard-wired to a battery provided in a sealed chamber within the tool.However, the wire leading to the switch on the external surface of thetool represents a leak path and potential failure point. Another knownswitch avoids the above problem by providing a mechanical switchcomprising two spaced electrical contacts in the tool that can be closedby an applied magnetic field. For example, a reed switch can be embeddedin a sidewall of a tool and a cutaway portion can be provided in theexterior of the tool allowing a magnet to be inserted therein to operatethe reed switch. This is advantageous as there is no leak path to theexterior of the tool. However, the reed switch itself is a mechanicaldevice and is especially prone to vibration or corrosion, which can be asource of failure.

According to a first aspect of the invention, there is provided aswitching device for a downhole tool, the switching device comprising anelectronic switch for accommodation within a downhole tool and anactivator for remote switching of the electronic switch.

Preferably, the activator is adapted for wireless activation of theelectronic switch. Preferably, the activator is constructed to enablecontactless activation of the electronic switch.

The electronic switch can be switched between an active and an inactiveconfiguration. The electronic switch can be switched between the activeand the inactive configurations by the activator.

Provision of the switching device according to the invention conservesbattery life of a tool and enables a tool to be switched “on” at surfacejust prior to being run downhole. An advantage of the invention is thatit provides a non-mechanical method of switching a tool “on” or into theactive configuration.

The electronic switch can comprise a closed electrical system with noexternal electrical connections. Preferably the electronic switchcomprises electrical components and no mechanical components.

The electronic switch can comprise an electronics module and a powersource.

In the active configuration, the switch can allow electrical connectionbetween the electronics module and the power source. In the inactiveconfiguration, the switch can prevent electrical connection between theelectronics module and the power source.

The electronics module and the power source can be housed within thetool. The electronics module and the power source can be housed within asidewall of the tool. The electronics module can comprise electricalcomponents arranged on a circuit board and the power source can be abattery.

The electronic switch can comprise an electronic latch, such that oncethe electronic switch is switched into the active configuration, theelectronic latch retains the electronic switch in the activeconfiguration. The electronic latch can form part of the electronicsmodule.

Since the electronic switch can be remotely switched using theactivator, there is no requirement for placement of a mechanical switchon the exterior of the tool.

The activator can energise part of the electronic switch in order thatthe activator can communicate with the electronic switch. The electronicswitch can comprise a receiver and the activator can energise thereceiver.

The receiver can be constructed and arranged to receive a signal fromthe activator. The receiver can be electrically connected to theelectronics module.

The activator can comprise a transmitter to transmit electromagneticenergy for remotely communicating with the electronic switch.

The receiver and the activator can be remotely communicable with oneanother. The receiver and the activator can be remotely communicableusing radio frequency identification.

The receiver and activator can be remotely communicable using afrequency in the range 20 Hz-600 kHz. The frequency selected for remotecommunication can be in the range 50 Hz-50 kHz.

The communication frequency of the activator and the receiver of theelectronic switch can be selected depending on the predeterminedlocation of the electronic switch within the tool. For example, a lowerfrequency is preferably selected where the receiver of the electronicswitch is surrounded by metal. Alternatively, the receiver can bearranged to form part of the throughbore of the tool and a higherfrequency can be selected for communication with the activator.

The receiver and activator can be remotely communicable using a resonantfrequency of the receiver. Communication at the resonant frequency isadvantageous since this allows optimum energy transfer between thereceiver and the activator. Furthermore, it increases the likelihoodthat the electronic switch will pick up a signal from the activator in ametal environment. Additionally, by requiring the electronic switch torespond to a resonant frequency supplied by the activator, thelikelihood of inadvertent actuation of the electronic switch by strayfrequencies is reduced.

The receiver can also act as a transmitter. The electronic switch canthereby transmit information to the activator. The electronic switch cancommunicate information regarding whether the electronic switch is inthe active configuration or the inactive configuration. The electronicswitch can communicate information such as a unique address allowingidentification and status of the tool.

The electronics module can include a rectifier to convertelectromagnetic energy received from the activator via the receiver intodirect current, which can then be used to switch the electronic switchinto the active configuration.

The receiver can be an antenna. The antenna can be a coiled conductor.The coiled conductor can circumscribe the throughbore of the tool. Thecoiled conductor can be coaxial with the throughbore of the tool.

Alternatively, the antenna can be provided in parallel to thethroughbore of the tool. The antenna can be housed within a sidewall ofthe tool.

The activator can also be configured to reprogram the electronic switch.The activator can be a hand held device. The activator can comprise avisual display.

The activator can be constructed for remote communication with theelectronic switch at surface.

The activator can be configured to test the tool prior to being rundownhole.

The activator can comprise a reader to receive information. The readercan be useful for reading the details/address of the electronics moduleof the electronic switch.

The activator can also be configured to reprogram the electronics moduleof the electronic switch.

The electronic switch can comprise a timer and the activator can commandthe switch into an active configuration, to be carried out after apredetermined time delay. The timer can form part of the electronicsmodule.

According to a second aspect of the invention, there is provided a toolfor use downhole, the tool accommodating the switching device of thefirst aspect of the invention.

The tool can be a downhole tool. The tool can have a throughbore and theactivator can be sized to travel within the throughbore of the tool,wherein the activator and the tool are arranged such that the activatoris inserted into the throughbore of the tool to activate the tool.

The receiver of the electronic switch can have a dual function and canalso act as a receiver for remote communication and/or actuation of thetool downhole.

The electronic switch can be accommodated within a sidewall of the tool.

According to a third aspect of the invention, there is provided acontactless and wireless method of activating a battery powered circuitcomprising:

-   -   electrically connecting the electronic switch to the battery        powered circuit; and    -   remotely switching the electronic switch using an activator and        thereby activating the battery powered circuit.

According to the third aspect of the invention, there is provided anapparatus for contactless and wireless activation of a battery poweredcircuit comprising:

-   -   an electronic switch electrically connected to the battery        powered circuit; and    -   an activator for remote switching of the electronic switch to        activate the battery powered circuit.

Preferably the apparatus and method according to the third aspect of theinvention are for powering a circuit in a downhole tool.

All features and steps of the first and second aspects of the inventioncan be combined with the third aspect of the invention whereappropriate.

Embodiments of the invention will now be described with reference to theaccompanying drawings in which:—

FIG. 1 is a schematic view of a switching device in accordance with theinvention showing an activator communicating with an electronic switchwithin a tool;

FIG. 2 is a schematic view of the switching device of FIG. 1 showing theelectronic switch communicating with the activator; and

FIG. 3 is an exploded view of an alternative embodiment of a downholetool incorporating an electronic switch.

A switching device is shown generally at 8 in FIGS. 1 and 2. Theswitching device 8 comprises an activator 20, which is preferably in theform of a handheld activator unit 20, and an electronic switch 111located within a downhole tool 100. The downhole tool 100 typicallycomprises OCTG pin and box screwthread connections to provide connectionto other components to allow the downhole tool 100 to be incorporated ina downhole string and preferably comprises a cylindrical mandrel (notshown) having a throughbore typically of an inner diameter no smallerthat the throughbore of the rest of the downhole string, and an outersurface with a sidewall therebetween.

The activator 20 includes a battery pack 26 electrically connected to anelectronics module 24 that is in turn electrically connected to anantenna 22. The activator 20 is a handheld unit with a display panel(not shown).

The battery pack 26 within the activator 20 is preferably selected toprovide as much power as possible since the activator 20 is used at, orcontrolled from, the surface of a downhole wellbore such as on adrilling rig or platform or the like. Therefore, the battery pack 26within the activator 20 can be removed and replaced as frequently asrequired. This is advantageous since the more powerful the battery pack26, the stronger the signal emitted by the antenna 22 and the greaterthe likelihood that the signal from the antenna 22 within the activator20 will be picked up by the electronic switch 111 within the downholetool 100.

Optionally, the activator 20 can be provided with an on/off switch suchas a mechanical switch (not shown) located on an external surface of theactivator 20 to conserve life of the battery pack 26 within theactivator 20 when the activator 20 is not in use. This is especiallyuseful when the activator 20 is intended for use at or near the surfaceof the downhole wellbore and therefore unlike the downhole tool 100 doesnot have to withstand high downhole temperatures and pressures andexposure to aggressive fluids.

The electronic switch 111 comprises the following components: areceiver/transmitter in the form of an antenna 112; an electronicsmodule 124; an actuator 118; and a power source in the form of a batterypack 126. These components form a closed electrical circuit and requireno external electrical connectors. The electronics module 124, actuator118 and battery pack 126 are housed within a sidewall of the tool 100.

The downhole tool 100 of FIGS. 1 and 2 has a throughbore (not shown).The antenna 112 is arranged to receive and transmit a radio frequencyidentification (hereinafter RFID) signal and is located in a sidewall ofthe tool 100 parallel to the throughbore. The antenna 112 iselectrically connected to the actuator 118 via the electronics module124. Initially, the electronic switch 111 is “off” or arranged in aninactive configuration, in which there is no electrical connectionbetween the electronics module 124 and the battery pack 126.

The electronics module 124 includes a rectifier to convert theelectromagnetic energy received from the antenna 112 as an alternatingcurrent into a direct current, which is in turn used to activate anelectronic latch such as a suitable transistor or the like (not shown)located on or within the electronic module 24 into the activeconfiguration. The electronics module 124 is electrically connected tothe battery pack 126 in the active configuration. Thus, on receiving thenecessary command via the antenna 112, the electronic latch instructsthe electronics module 124 and the battery pack 126 to turn “on” andmove into the active configuration in which there is electricalconnection between the electronics module 124 and the battery pack 126.The electronics module 124 can then provide power via wire 117 toactuator 118 either straightaway or after a period of time has elapsedor can alternatively power the antenna 112 to await further instructionfrom eg. an RFID tag (not shown) which is particularly possible with theRFID downtool™ system that could be used with the embodiment shown inFIG. 3 as will be described subsequently. The actuator 118 is any sortof electrically operated device that an operator wishes to be able tooperate such as a motor or sliding sleeve etc. It will be understood bythose skilled in the art that the wire 117 can be relatively short ifactuator 118 is located within downhole tool 100 or could be relativelylong if the actuator 118 is provided in an adjacent downhole componentin the string. In other words, the actuator 118 need not be included inthe same downhole tool 100 as the antenna 112 and/or electronics module124 if suitable wire connections 117 are provided.

The electronics module 124 also includes transistors and othersemi-conductors arranged on a circuit board so as to create anelectronic latch and ensure that the electronic switch 111 remains inthe active configuration once the electronics module 124 is connected tothe battery pack 126.

The advantage of using electronic components suitably interconnected ona circuit board within the electronics module 124 in order to switchbetween the inactive and the active configuration (and subsequently toretain the electronic switch 111 in the active configuration) is thatsemi-conductors and other electronic components are very reliable in ahigh vibration environment, thereby alleviating many of the problemsassociated with conventional mechanical switches.

The antenna 22 of the activator 20 and the antenna 112 of the electronicswitch 111 communicate at a specific radio frequency (RF) signal.According to the present embodiment, the communication frequency isselected as the resonant frequency of the antenna 112, having a value ofaround 125 kilohertz. Communication using RF signals at the resonantfrequency allows optimum energy transfer between the activator 20 andthe antenna 112 of the downhole tool 100. Another advantage of makinguse of the resonant frequency is that it enhances the likelihood of theantenna 112 picking up a signal in the metal environment of the downholetool 100 and thus makes the most of the very low energy that will beoutput by the antenna 112 to activate the electronic latch.

Typically, the downhole tool 100 is assembled onshore and the antenna112, electronics module 124, actuator 118 and battery 126 making up theswitching device 111 are sealed within the sidewall of the tool 100.Initially, the electronic switch 111 is in the inactive configurationand the battery pack 126 is not in electrical connection with theelectronics module 124. The downhole tool 100 can then be transportedoffshore in the inactive configuration until it is ready for usedownhole. Therefore the power of the battery pack 126 is conserved.

When an operator wants to run the tool downhole, the operator will needto switch the electronic switch 111 into the active configuration. Ifthe activator 20 has a switch, it is switched on so that the antenna 22emits electromagnetic energy in the form of an RF signal at the chosenfrequency as shown schematically at 31 in FIG. 1. The activator 20 isplaced in the throughbore of the downhole tool 10 by the operator andtravels along the length of the downhole tool 100 in the throughbore.During passage of the activator 20 through the tool 100, the antenna 22energises the antenna 112 of the downhole tool 100 by emitting theresonant RF signal. The rectifier in the electronics module 124 uses theresultant direct current to activate the electronic latch/transistor inthe switch 111 into the active configuration. In other words thelatch/transistor in the electronic module 124 is switched on by thevoltage provided by the antenna 112 and once it is switched on, thebattery 126 and said transistor latches the electronic module 124 in theon configuration. In the active configuration, the battery pack 126 iselectrically connected to the electronics module 124 and thereforepowers the same. The electronics module 124 is latched in the activeconfiguration by the electronic latch in the form of semi-conductors inthe electronics module 124.

Once the battery pack 126 is electrically connected with the electronicsmodule 124, it can supply power to the electronics module 124 forpowering further operations of the downhole tool 100.

The antenna 22 of the activator 20 can also be configured for use as areceiver. Immediately following the energising of the antenna 112 of thedownhole tool 100 and switching of the electronic switch 111 into theactive configuration, the antenna 22 can receive signals (shownschematically as 33 in FIG. 2) transmitted from the antenna 112 of thedownhole tool 100. The activator 20 can read information transmittedfrom the electronics module 124, such as the specific electronic addressallotted to each tool 100. This enables easy identification of thespecific downhole tool 100 on the display panel of the activator 20. Theactivator can then change the tool address if necessary.

The activator 20 can also collect information regarding the programmingof the electronics module 124 before the tool 100 is run downhole. Theactivator 20 can be used to reprogramme the electronics module 124 inresponse to changing requirements or conditions offshore just prior torunning the tool 100 downhole. Additionally, the activator 20 can testthe tool 100 before the tool 100 is run downhole. This is especiallyuseful for the testing of reversible operations of the downhole tool 100to ensure that the tool 100 is functioning correctly.

According to the embodiment described above, the antenna 112 of thedownhole tool 100 is parallel with the throughbore. However, in thealternative embodiment shown in FIG. 3, the antenna forms part of theinner diameter of the tool 40 and surrounds the throughbore. This isadvantageous as the antenna can be readily used for another application,such as remote communication using RFID downhole™ (Trade Mark) followingthe remote switching of the tool at surface.

An exterior of a substantially cylindrical hollow tool 40 is shown atFIG. 3. The tool 40 has a throughbore 41 and circumferentially spacedbores 54, 56, 59 drilled in a sidewall of the tool parallel to thethroughbore 41. The cylindrical bore 54 receives an electronics module44 in the form of a cylindrical tube. The cylindrical bore 56 receives abattery pack tube 46 and the cylindrical bore 59 receives an actuator inthe form of a motor 49. The motor 49 is provided to allow the tool 40 toperform a downhole operation. All of the cylindrical bores 54, 56, 59are electrically connected to one another to electrically connect thebattery pack tube 46, the electronics module 46 and the motor 49.

An antenna 42 is inserted within the throughbore 41 of the tool 40. Theradio frequency identification (hereinafter RFID) antenna 42 has athroughbore 43. The RFID antenna 42 is cylindrical and comprises aninner liner and a coiled conductor in the form of a length of copperwire that is concentrically wound around the inner liner in a helicalco-axial manner. Insulating material circumscribes an exterior of thecoiled conductor. The liner and the insulating material are formed froma non-magnetic and non-conductive material such as fibreglass, rubber orthe like. The RFID antenna 42 is formed such that the insulatingmaterial and the coiled conductor are sealed from the outer environmentand the throughbore. The antenna 42 forms part of an inner diameter ofthe tool 40.

According to the present embodiment a high communication frequency (forexample 100 kilohertz) is selected for communication between the antenna42 of the tool 40 and the activator 20. Selection of higher frequenciesis possible since the antenna 42 is not separated from the throughbore43 by metal. This is in contrast to the previous embodiment where theantenna 112 is housed within a side wall of the tool 100. Lowerfrequencies (for example, those above around 20 hertz) are more suitableif there is significant amount of metal in the side wall of the toolbetween the antenna 12 and the throughbore.

In order to switch the tool 40 of FIG. 3 into the active configuration,the activator 20 is run along the throughbore 43 of the tool 40. Theantenna 22 of the activator 20 energises the antenna 42 to send a signalto the electronics module tube 44 and activate the switch in the samemanner as previously described for the first embodiment.

The RFID antenna 42 surrounding the throughbore is a preferredarrangement for receiving a signal from the activator 20 because theantenna 42 entirely surrounds the activator 20 when located in thethroughbore 43 and there is no metal located therebetween.

The present invention is more reliable than a mechanical switch.

Modifications and improvements can be made without departing from thepresent invention. For example, the activator 20 can be attached on awireline and run to a downhole location in order to activate theelectronic switch 111. Certain modifications would be required to theactivator 20 in order to ensure it is suitable for use downhole.

The invention claimed is:
 1. A method of activating a downhole tool foruse in an oil, gas or water well, wherein the downhole tool has anelectronics module, a battery, a tool antenna, and an actuator forming aclosed electrical circuit in the downhole tool with no externalelectrical connections; and wherein the method includes the step ofswitching the closed circuit to an active configuration prior to runningthe downhole tool into the well, wherein the step of switching to theactive configuration comprises energizing the tool antenna in responseto a signal received from an activator when the activator is passedthrough the tool throughbore adjacent to the tool antenna.
 2. The methodof claim 1, wherein the downhole tool has a sidewall surrounding a toolthroughbore, and wherein the tool antenna is disposed in the cylindricalsidewall.
 3. The method of claim 1, wherein the antenna surrounds thetool throughbore.
 4. The method of claim 1, wherein the tool antenna isexposed to the tool throughbore.
 5. The method of claim 1, wherein thetool antenna comprises a coiled conductor sealed from the toolthroughbore by non-magnetic and non-conductive material.
 6. The methodof claim 1, wherein the tool antenna is cylindrical and forms a part ofthe tool throughbore.